The high incidence of lung cancer and the poor survival rate make lung cancer a very important public health problem, and the leading cause of cancer death in the world. Most patients have locally advanced lung cancer at the time of diagnosis. As per the Madras Metropolitan Tumour Registry (MMTR) Chennai, in 2006-2008, cancer of the lung was the most common among males, and was ranked among the top ten in females.
It constituted 10.9 per cent and 3.3 per cent of all cancers among males and females respectively. The peak incidence occurred in the age group of 65-69 years among both sexes.
Cigarette smoking is the single highest cause of the lung cancer epidemic.
Other contributing factors are asbestos, arsenic, chromium, nickel, and radon in the work environment.
Other environmental factors such as passive smoking and air pollution.
Molecular changes that commonly occur in lung cancer are mutations of tumour suppressor genes p16, p53, and H, K, N-ras family of oncogenes.
Studies have shown that individuals with a higher dietary intake of fruits or vegetables have a lower risk of lung cancer.
Lung cancers are classified into:
- Non-Small Cell Carcinoma (NSCLC) includes squamous cell carcinoma, adenocarcinoma, large cell carcinoma and their subtypes (80 per cent).
- Small Cell Carcinoma (SCLC) (20 per cent).
- There are other rare types of lung cancers that can occur apart from these.
Well-differentiated squamous cell carcinomas and non-mucinous bronchioalveolar carcinomas have a favourable prognosis.
Poor prognostic factors include higher tumour size and extent, regional nodal involvement, absence or presence of distant metastasis, weight loss of more than 10 per cent, age less than 40 years, tumour size more than 3 cm, Lymphovascular invasion, and mutation of the tumour suppressor gene p53.
Spread can occur along the bronchus into lung parenchyma, to mediastinum or pleura causing pleural effusion. Diaphragm and chest wall involvement are not uncommon. 50 per cent have nodal metastasis at resection. Distant spread commonly involves the adrenals to 50 per cent, liver to 30 per cent, apart from the brain, bone opposite lung, pericardium and kidneys.
Cough, weight loss, chest pain, shortness of breath, blood in the sputum, superior vena cava syndrome, ulnar nerve and Horner’s syndrome (Pancoast tumour) are common symptoms of lung cancer.
Screening for lung cancer
At present, screening for early detection of lung cancer is not recommended, probably because of the failure of early studies to demonstrate any mortality reduction from lung cancer evaluation based on sputum cytology and/or chest radiography. With the introduction of helical computerised tomography, a new imaging modality that can detect nodules as small as a few millimetres, the potential benefits of lung cancer screening are being re-examined.
Imaging in lung cancer
Chest radiography remains the basic modality for the detection of lung cancer.
Computerised tomography (CT) provides information about the primary lesion, thoracic lymph nodes, pleura, chest wall and upper abdomen. It is the standard imaging modality for staging lung cancer.
Magnetic resonance imaging (MRI) appears to be superior to CT in detecting mediastinal, chest wall tumour invasion into the pericardium, heart and great vessels, brachial plexus, vertebral body and spinal canal.
Positron emission tomography (PET) is a molecular imaging modality that detects metabolic changes in tumour cells. PET improves the rate of detection of the extent of the primary tumour, draining nodes and distant metastases thereby improving the staging accuracy in patients with NSCLC which can have a significant impact on clinical management.
Other diagnostic modalities
Clinical and radiological findings should guide the diagnostic approach, depending on the size and location of the tumour, the presence of metastatic disease, and the clinical status of the patient. Diagnostic and staging work is taken up concomitantly.
Sputum cytology, flexible bronchoscopy for biopsies, brushings and washings, CT-guided transthoracic needle aspiration, oesophageal endoscopic ultrasound-guided fine needle aspiration/trust biopsy of the mediastinal nodes, anterior mediastinoscopy to assess lymph nodes, are the aids used to establish the histopathological diagnosis. Distant metastatic sites need to be documented with microscopic diagnosis.
- Surgery is the preferred modality of primary management for resectable NSCLC.
- Based on the initial stage and postoperative histopathological report, patients will be planned for adjuvant radiation therapy with or without chemotherapy or chemotherapy with or without radiation therapy.
- For medically inoperable and unresectable tumours chemoradiation therapy is the preferred line of management.
- With the rapid technological explosion in diagnostic imaging and radiation delivery techniques, radiation oncologists are now able to deliver external beam radiation therapy with high precision using Image Guided Intensity Modulated Radiation Therapy (IG IMRT), Stereotactic Body , Radio surge with real-time positional management respiratory gating system delivering significantly higher doses to the tumour and minimum dose to the surrounding normal lung and other critical structures like the opposite lung, heart, spinal cord, oesophagus, and breast, resulting in increased cure rates and lesser side effects respectively.
- Radiation along with chemotherapy has a role in the palliation of symptoms due to recurrent, advancing and metastatic cancer.
- Newer targeted therapy compounds have resulted in progression-free and overall survival advantages in NSCLC.
- For SCLC, chemoradiation therapy is the preferred choice of treatment, except in T1-2 NO MO where surgery followed by chemotherapy is the standard of care.
The by and large outcome for patients with lung cancer may not be gratifying at present. But with improved surgical techniques, newer anti-cancer drugs, and modern radiation therapy delivery techniques, we are able to confer superior progression-free and overall survival periods ensuring a good quality of life for our patients. Lung cancer surgery Doctors in India attracts many international patients because of availability of very good treatment facilities, good success rate and very low cost of treatment.